SE528778C2 - A method and a control unit for determining the opening temperature of a temperature controller - Google Patents

Abstract

Method for determining the opening temperature of a temperature controller comprises regularly measuring the temperature of coolant and storing a recorded local maximum temperature value and determining the opening temperature as a recorded local maximum temperature value which is stored in the storage unit. Independent claims are also included for the following: (1) Computer program for determining the opening temperature of a temperature controller, for controlling the revolutions of a fan and for estimating the degree of action of an intermediate cooler; (2) Control unit for determining the opening temperature of a temperature controller, for controlling the revolutions of a fan and for estimating the degree of action of an intermediate cooler; (3) Vehicle.

Description

25 30 528 778 Furthermore, directives within the EEC (European Economic Community, EEC) have been developed for various types of regulation of environmentally harmful emissions. Directive 88/77 / EEC requires all motor vehicles equipped with compression-ignition engines and gaseous emissions to be fitted with an on-board diagnostic (OBD) system from 1 October 2005.

The Directive defines an OBD system as an emission control system with the ability to detect the presence of a malfunction and to identify the probable area of the malfunction through error codes stored in a computer memory.

There are different legal requirements for these OBD systems. For example, they must fulfill certain functions and periodically perform various tests.

An OBD system must, among other things, indicate a malfunction of an emission-related component when the malfunction results in an increased emission above different threshold values, eg emissions of nitrogen oxides (NOX) should not exceed a predetermined limit value.

An example of what can be monitored is the external temperature sensor. It is very important that the signal from the external temperature sensor shows a value that is as accurate as possible to meet the requirements for OBD systems according to the EU directive.

A method for monitoring the function of the external temperature sensor has been shown in the Swedish patent application SE 0400443-8, relating to the present application, which is hereby incorporated by reference. The described method is based on the assumption that a very high efficiency of the charge air cooler (intercooler) can be verified 528 778. This can be done by determining the speed of the internal and external air flow of the charge air cooler.

EP 1 201 890 describes a system for monitoring the differences in temperature over a charge air cooler. The system is used to determine if the charge air cooler is not working satisfactorily. The variables measured are outside temperature (Tæm) and temperature after the charge air cooler (Tmm fi) and according to the established formula for the efficiency of the charge air cooler: Tham: = The -Û (Thc "Tàm) (1) At a high efficiency nal, then Tmwü e Tmm ( This is a simple way to verify that the charge air cooler has a high efficiency provided that the accuracy of the external temperature sensor is sufficient.On the other hand, and if the external temperature sensor is to be monitored, the efficiency of the charge air cooler must be determined differently.

Thus, there is also a need to further improve the possibility of verifying a high efficiency in the charge air cooler, especially before the function of the external temperature sensor is monitored as shown in the above-mentioned Swedish patent application SE 0400443-8.

Both the needs mentioned above can be addressed if the function of the temperature controller in the cooling loop is examined.

SUMMARY OF THE INVENTION A first object of the invention is to provide a method and a control unit for determining the opening temperature of a temperature regulator in a cooling loop, which opening temperature can be used to determine the cooling capacity of the coolant and overcome the problems mentioned above.

This first object is achieved by a method according to the characterizing features as defined in claim 1 and a control unit as defined in claim 20.

A second object of the invention is to provide a method and a control unit for speed control of a fan which will provide a vehicle with lower fuel consumption compared to previously known vehicles.

This second object is achieved by a method according to the characterizing features as defined in claim 8 and a control unit as defined in claim 21.

A third object of the invention is to provide a method and control unit for continuously estimating the efficiency of a charge air cooler, providing cooled air to an engine, and providing an indication that the efficiency of the charge air coolers is sufficiently high without estimating the internal and / or external air flow of the charge air cooler.

This third object is achieved by a method according to the characterizing features as defined in claim 11 and a control unit as defined in claim 22.

A fourth object is to provide a vehicle with a control unit for determining the opening temperature of the temperature controller and / or controlling the speed of a cooling fan during operation.

This fourth object is achieved by a vehicle according to the characterizing features as defined in claim 23.

A fifth object is to provide a vehicle with a control unit for continuously estimating the efficiency of a charge air cooler, providing cooled air to an engine, during operation.

This fifth object is achieved by a vehicle according to the characterizing features as defined in claim 24.

Furthermore, it is an object to provide a computer program which implements each of the methods and which is executed in the respective control unit, and to provide computer program products which are adapted to store the computer programs.

This object is achieved by a computer program as defined by the characterizing features of claims 16, 17 and 18, and by a computer software product as defined by the characterizing features of claim 19.

The method according to the invention can be briefly described as the use of an outlet temperature sensor for the coolant in the engine to determine the opening temperature of a temperature regulator in the cooling coil of the engine.

In ordinary vehicles, a fan is placed near the radiator to direct air flow through the radiator to cool the coolant for cooling the engine during operation. If the temperature controller is closed, the coolant is directed through the bypass channel (bypass) and there is no need to rotate the fan. However, if the coolant has a higher temperature than the opening temperature of the temperature regulator, then a more efficient cooling in the cooler can be performed by using a high speed rotating fan.

Furthermore, the charge air cooler, if present, is located in front of the cooler in the cooling coil and the engine's ability to cool the coolant can thereby be used as an indication that the efficiency of the charge air cooler is high.

If the coolant gets hot, the coolant does not cool satisfactorily, which in turn means that more energy is supplied to the engine than can be cooled off. If this is the case for the coolant, the same may apply to the charge air cooler. This information could, for example, be used to avoid performing a test of the external temperature sensor as described in the Swedish patent application SE 0400443-8.

An advantage of the present invention is that a better estimate of the opening temperature can be used to control other systems in the engine, ie existing hardware can be used to verify a high efficiency.

Another advantage is that fuel consumption can be reduced if the speed of the fan is controlled more efficiently.

Another advantage of the present invention is that a better estimate of the efficiency of the charge air cooler can be obtained without costly reconstructions of existing engine systems, ie existing hardware can be used to verify a high efficiency. Another advantage of the present invention is that the driver can quickly and easily receive information regarding a charge air cooler with a malfunction, and in a preferred embodiment can also receive correct information about an external temperature sensor with a function interruption based on the assumption that the charge air cooler is in operation. with an efficiency close to 1.

Additional objects and advantages may be obtained from the detailed description of the invention described in conjunction with the accompanying drawings, provided by way of non-limiting example.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a first embodiment of a system according to the present invention.

Fig. 2 shows a second embodiment of a system according to the present invention.

Fig. 3 shows a flow chart for speed control of a fan and for estimating the efficiency of a charge air cooler.

Fig. 4 shows a flow chart of a first embodiment for determining the opening temperature of a temperature controller.

Fig. 5 shows a flow chart of a second embodiment for estimating the opening temperature of a temperature controller. Fig. 6 shows a flow chart of a third embodiment for estimating the opening temperature of a temperature controller.

Fig. 7 shows a temperature curve of a temperature controller to illustrate the methods according to the invention.

Figs. 5a and 8b show vehicles provided with control units carrying out the methods according to the invention.

EMBODIMENT FOR CARRYING OUT THE INVENTION Fig. 1 shows an embodiment of a system 10 for speed control of a fan 18. The system comprises a motor 14, a radiator 19 'with a cooling coil 19, the fan 18 and a control unit 15. Air, with a temperature Inch (outside temperature), supplied to the engine 14. The exhaust gas is emitted from the vehicle exhaust system. The engine 14 is provided with the cooling coil 19, comprising coolers 19 ', a bypass duct 8, and a temperature regulator 9, for cooling the engine by using a coolant. A temperature sensor 16 is arranged to measure the temperature (Tmxmà of the coolant in the engine 14).

When the temperature regulator 9 is closed, the coolant circulates through the bypass channel 8, but when the temperature regulator 9 is open, the flow of coolant is controlled through the cooler 19 '.

The cooling capacity of the radiator depends mainly on the external air flow 17, and the speed of the external air flow 17 is in this embodiment controlled by the speed of the fan 18.

The function of the cooling coil also depends on a properly functioning temperature controller 9.

The control unit 15, which comprises a microprocessor uP together with memory M, gathers necessary information from the system to carry out the method according to the invention. In this embodiment, signals from the temperature sensor for the coolant 16 are fed to the control unit 15 through a connection 16 ', and signals from the fan 18 are fed as an optional alternative to the control unit through connection 18'. The control unit is also provided with means for controlling the speed of the fan 18 by using a communication line 18 ". The control unit 15 comprises at least one computer program product, preferably in the form of a memory M, such as ROM (Read Only Memory). PROM (Programmable ROM), EPROM (Erasable PROM), EEPROM (Electrically EPROM), flash memory, SRAM (Static Random Access Memory), etc. A computer program 5 is stored in the memory M and the control unit, when the program is executed in the microprocessor pP, can perform the method of controlling the speed of the fan 18 to increase the efficiency of the motor 14, and as an optional alternative, performing a method of determining the opening temperature of the temperature controller 9.

Fig. 2 shows an embodiment of a system 20 for estimating the efficiency of a charge air cooler 13, and also for monitoring an external temperature sensor 11. The system comprises a turbo 12, comprising a compressor C and a turbine T, the charge air cooler 13, an engine 14, a cooler 19 'with a cooling coil 19 and a control unit 15. Air, with a temperature Tæm (outside temperature) enters the compressor C, pressurized and the air temperature is thus increased to TM; (temperature after compressor). The air with the increased temperature is then fed to the charge air cooler 13.

The air is cooled to a lower temperature, Tmmü, in the charge air cooler 13 and then fed to the engine 14. The exhaust gas from the engine 14 is fed to the turbine T which drives the compressor C, and is later discharged from the vehicle exhaust pipe. The motor 14 is provided with the cooling coil 19, comprising the cooler 19 ', a bypass duct 8 and a temperature regulator 9, for cooling the engine by using a coolant. A temperature sensor 16 is arranged to measure the temperature (Tmxm) of the coolant in the engine 14.

When the temperature regulator 9 is closed, the coolant circulates through the bypass channel 8, but when the temperature regulator 9 is open, the flow of coolant through the cooler 19 'is controlled.

The cooler 19 'and the charge air cooler 13 are arranged in such a way that the coolant in the cooling coil 19 and an internal air flow through the charge air cooler 13 are cooled by an external air flow 17. The inner cooled air flowing through the charge air cooler is fed to the engine 14. the cooling capacity of the radiator, depends mainly on the external air flow 17. The function of the cooling coil also depends on a properly functioning temperature regulator 9. The external air flow 17 can be determined from the speed v of the vehicle and / or by using the number of rotations of a fan 18 of the engine 14 and / or other arrangements.

The control unit 15, which comprises a microprocessor pP together with a memory M, collects necessary information from the system to perform the method. In this embodiment, signals from the temperature sensor for the coolant 16 and the external temperature sensor 11 are connected to the control unit 15 through the connections 16 'and 11', respectively. The control unit comprises at least one computer program product, preferably in the form of a memory M, such as ROM (Read Only Memory), PROM (Programmable ROM), EPROM (Erasable PROM), EEPROM (Electrically EPROM), flash memory, SRAM (Static Random Access Memory), etc. A computer program 5 is stored in the memory M and the control unit, when the program is executed in the microprocessor uP can perform the method of estimating the efficiency of the charge air cooler, and as an optional alternative to perform a method of determining the opening temperature of the temperature controller 9. When the efficiency of the charge air cooler is acceptable, the computer program can verify the function of the external temperature sensor 11 as described in the Swedish patent application SE 0400443-8.

The control unit can also collect information regarding, for example, the number of rotations of the engine 14 through the connection 14 'and fuel consumption of the engine through the connection 14'.

The control unit 15 will emit some kind of alarm, for example if the efficiency of the charge air cooler 13 is too low, or if the external temperature sensor 11 has a malfunction.

Fuel consumption is used to determine that the temperature after the compressor (TMJ is low enough to perform the procedure of verifying the function of the external temperature sensor 11 if the efficiency of the charge air cooler 13 is sufficiently high. Further details of the procedure to verify the external temperature sensor can be found in the patent application SE 0400443-8.

Fig. 3 shows a flow chart describing a method for speed control, eg increasing the number of rotations, of a fan in a system as shown in Fig. 1, or for estimating the efficiency of a charge air cooler in a system as shown in Fig. 2.

The flow starts in step 30 and proceeds to step 31, where the opening temperature Iwm1hos the temperature regulator 9 in the cooling coil 19 is determined. The aperture temperature could be a fixed value provided by the manufacturer of the temperature controller 9, or a previously stored value in the memory of the control unit 15, but usually the aperture temperature must be measured regularly as it can vary. Methods for determining the orifice temperature will be described in connection with Figures 4, 5 and 6.

The value of the set opening temperature is normally measured when starting the engine and then stored in the memory M of the control unit 15.

In step 32, the temperature Tmxm 2 of the coolant in the engine 14 is measured by using a temperature sensor 16. The value can be saved in the memory M of the control unit 15.

When the value of the opening temperature Tqmn has been stored in the memory M and the coolant temperature Tmmæ has been measured, the difference between them is compared with a temperature limit value Tnmü> 0 in step 33. If Tmmm ~ Tqæn> Thmü the flow is fed to step 34, where the speed of the fan 18 can be controlled because the coolant passes through the cooler 19 'and / or an alarm indicating low efficiency of the charge air cooler 13 is issued. The flow then proceeds to step 35. On the other hand, on Tmmmr-TqænšT1nüt, the flow proceeds to step 35.

If the opening temperature Tqæn is determined using a method as described in connection with Figures 4, 5 and 6, and if it is decided that Tqæn is to be updated in step 35, the flow is fed back to step 31. On the other hand, if an update of the opening temperature Tqæn is not possible (in the case of a fixed value) or if it is not necessary, the flow is fed back to step 32 where a new measurement of the coolant temperature Ewan is performed. 10 15 20 25 30 CH RQ OC 13 An update of the opening temperature, if possible, is normally performed at regular intervals, eg 2-4 hour intervals.

The temperature of a temperature controller 9 is normally in the temperature range of 80-90 ° C, and a typical value is about 85 ° C. An example of a temperature value Tumü to determine that the coolant flows through the cooler 19 'is> 0 ° C.

Another example of a temperature limit value Thin for estimating the efficiency of a charge air cooler 13 is between 1.5 - 2 ° C. This will indicate for a typical charge air cooler an efficiency of the charge air cooler of more than 99% (> 0.99), which is sufficient to proceed with the function test of the external temperature sensor 11 as mentioned above.

Fig. 4 shows a first embodiment for determining the opening temperature T @ m, of the temperature controller 9 (step 31 in Fig. 3) if the opening temperature T

The temperature of the coolant Emm, is measured in step 41, and in step 42 a decision is made whether the measured Ihmwr is a local maximum temperature value T¿æJTmmJ or not. If the measured value of Tmww is not a maximum value, the flow is fed back to step 41 and a new measurement of Tmmw is made. On the other hand, if the measured value of Tmmm is a maximum value, the value is saved in a memory space in the memory M and the flow continues to step 43. In step 43, the opening temperature Tqæn is set to the saved local maximum temperature value I fi ædïhmmr). The flow then proceeds to step 32 in Fig. 3.

Fig. 5 shows a second embodiment for determining the opening temperature Tqæn of the temperature controller 9 (step 31 in Fig. 3) if the opening temperature Tqmn is not known in advance. A memory space, such as a vector V, is cleared in step 51 and the coolant temperature Tmxm is then measured in step 52. In step 53, a decision is made as to whether a local extreme (maximum Tum or minimum Tm fl) temperature value has been found. . If an extreme has been found, the flow proceeds to step 54 and the extreme is saved in the memory space V, if not, the flow is fed back to step 52 to measure another Tmtm. A minimum temperature value Tmm is always followed by a maximum temperature value TW, and vice versa, as illustrated in Fig. 7.

In step 55, a decision is made as to whether enough extremes have been found and saved. If not, the flow is fed back to step 52 and a further extreme is sought. If a sufficient number of extremes have been found, the flow proceeds to step 56 and the temperature difference Tdüf between all successive extremes, stored in the memory space V, is calculated. If any Td fi f is lower than a preselected lower temperature limit Tkm, the flow is fed back from step 57 to step 51, where the memory space is cleared and the process begins again. On the other hand, if no Td fi f is found to be lower than Thw (in step 57), the flow proceeds to step 58. If any Td fi f is higher than a preselected upper temperature limit, Typm, the flow is fed back from step 58 to step 51, where the memory space cleared and the process resumed. On the other hand, if no Tdüf is found to be higher than Tmgh (in step 58), the flow continues to step 59, where the opening temperature Tqæn is set to the maximum of the saved Bmx in the memory space. The flow then proceeds to step 32 in Fig. 3.

Fig. 6 shows a flow chart of a third embodiment for determining the opening temperature Tqæn of a temperature controller 9. This is an expanded variant of the flow chart described in connection with Fig. 5 and similar steps have been denoted by the same reference numerals for the sake of clarity.

Time counters Rmp and Rdmm are reset in step 61 before the memory space V is cleared in step 51. The flow continues with step 52 where the temperature of the coolant is measured and the counters are then counted before a decision is made in step 63 whether a maximum temperature value T¿u has been found or not. If a maximum value is found, the flow proceeds to step 67 and the Rdmm counter is reset before the flow proceeds to step 68.

If no maximum value has been found, the flow proceeds to step 64 where a decision is made as to whether or not a minimum temperature Tmn has been found. If a minimum value has been found, the flow proceeds to step 65 and the counter Km is reset before the flow proceeds to step 66. If no minimum value has been found, the flow is fed back to step 52 to measure an additional TNOÉ Or 'In step 66, a decision is made whether a down-time tmwn calculated by Rdmm is within a permissible range (tdwm¿ @ w: tdwm¿ fi g5 or not. If tdmm is OK, the flow proceeds to step 54 and Tm fl is saved in the memory space V, if not, the flow is fed back to step 51 to clear the memory space and restart the process of determining the opening temperature of the temperature controller.

In step 68, a decision is made as to whether an up-time tup, calculated by Rq, is within a permissible range (tuplm fi tuphmh) or not. If mm is OK, the flow continues to step 54 and Emx is saved in the memory space V, if not, the flow is fed back to step 51 to clear the memory space and restart the process of determining the opening temperature of the temperature controller.

In step 55, a decision is made as to whether or not enough extremes have been found. Preferably, at least five extremes are found and stored before the flow proceeds to step 56 where the differences between all successive extremes are calculated, otherwise the flow is fed back to step 52 to find an additional extreme. If any Tgüf is lower than a preselected lower temperature limit, Tmw, the flow is fed back from step 57 to step 51, where the memory space is cleared and the process begins again. On the other hand, if no Td fi f is found to be lower than Tkm (in step 57), the flow continues to step 58. If any T fi ff is higher than a preselected upper temperature limit, Tmmh, the flow is fed back from step 58 to step 51, where the memory space is cleared and the process begins again. On the other hand, if no Tdüf is found to be higher than Tmgh (in step 58), the flow continues to step 59, where the opening temperature Twm, is set to the maximum of the saved TW in the memory space.

The flow then proceeds to step 32 in Fig. 3.

If an opening temperature could not be determined for a predetermined time tlmm, eg tlmw = 2 hours, the process to verify the external temperature sensor is performed without having verified a correct opening temperature.

The reason for setting an allowable interval (tdmm¿ @ w: tmmmhwh) for downtime tmwn, and an allowable interval (tflmlm fi tughmh) for uptime if is as follows. The opening time and closing time of a temperature controller may vary depending on the design of the temperature controller. Normally wax, which melts and solidifies, is used to open and close the regulator. Long cooling coils also affect the allowable time intervals.

The temperature range for the allowable range TkW: Tmg, is widely dependent on the varying length of the cooling coil, which of course introduces inertia into the system. To illustrate the invention using the three embodiments described in connection with Figures 4, 5 and 6, an example of a temperature curve 70 is shown in Figure 7. The curve 70 is arranged in a 2-dimensional coordinate system with time. t [seconds] on the x axis and the temperature T [° C] on the y axis- Each extreme value is marked with a cross on the temperature curve 70 and numbered in sequence 1 to 5. Table 1 shows each temperature value and time together with the calculated uptime / down time. n Extrem. Tn [° C] tn tup Camm 1 Max 88.3 7 sec - - 2 Min 84.1 55 sec - 48 sec 3 Max 89.2 84 sec 29 sec ~ 4 Min 85.0 119 sec - 35 sec 5 Max 89 , 8 143 sec 24 sec - Table 1 EXAMPLE 1 Using the first embodiment of the method for determining the opening temperature of the temperature controller, as described in connection with Fig. 4, will result in Tqæn being equal to the measured temperature for the maximum temperature value at tl , i.e. Tqmn = 88.3 ° C.

EXAMPLE 2 The second embodiment of the method for determining the opening temperature of the temperature controller, as described in connection with Fig. 5, will need further calculations before the opening temperature can be determined. The absolute difference between all subsequent extremes is presented in Table 2. n | Tn-Tn-1 | 1 _ 2 4.2 ° C 3 5.1 ° C 4 4.2 ° C 5 4.8 ° C Table 2 All differences in temperature between the extremes are within a preferred temperature range TkW = 1 ° C, and Th @ h = 7 ° C, which means that Tqæn is equal to the measured temperature for the maximum temperature value at t3, ie Tqæn = 89.2 ° C, if only three extremes (n = 1-3) are chosen to be suitable for saving in the memory space before Tqmn is determined .

EXAMPLE 3 The third embodiment of the method for determining the opening temperature of the temperature controller, as described in connection with Fig. 6, will need the calculations presented in Table 2. In addition, the uptime and downtime presented in Table 1 must also be considered for the opening temperature. .

Assume: TkN = 1 ° C and Th¿m = 7 ° C, as in Example 2, and also that twhkW = 22 seconds, nm¿ fi @ = 7 0 seconds, tümmlmplß seconds and tmmmhÉh = 45 seconds. 10 15 25 25 25 528 778 19 Three extremes are chosen to be suitable for saving in memory space before Tqæn is determined, but the other extreme (n = 2) will not be allowed because the downtime tdmm = 48 Seconds is greater than the maximum allowed tmwmhmh = 45 seconds.

The memory space is thus cleared and the procedure for determining the opening temperature is restarted. Tqæn is determined after three extremes to be the measured temperature for the maximum temperature value at ts, ie Tqæn = 89.8 ° C.

In Fig. 8a, a vehicle 80 is provided which is provided with a control unit 15 and an engine 14 with a cooling coil 19, comprising a cooler 19 'and a temperature regulator 9, in a front part 81 of the vehicle. The vehicle could also be provided with a charge air cooler 13 depending on the application of the present invention. This type of vehicle is normally a truck, but buses can also have the engine 14 arranged in a front part of the bus. In this case, the velocity v of the vehicle is the dominant part of the cooling air flow provided to the radiator 19 'and the charge air cooler 13.

Fig. 8b shows a vehicle 83 which is provided with a control unit 15 in a front part 81 of the vehicle 83 and an engine 14 with, or without, a charge air cooler 13 depending on the application of the invention, placed in a rear part 82 of the vehicle. This type of vehicle is normally a bus, where the speed of the fan 18 is the dominant part of the cooling air flow.

The method according to the invention is preferably performed as a computer program implemented in the control unit. In addition, the computer program may be stored on a computer software product, such as a CD-ROM, magnetic tape, floppy disk, hard disk, etc.

Claims (24)

10 l5 20 25 30 528 778 20 P A T E N T K R A V A method for determining the opening temperature (TWÜQ of a temperature controller (9) in a vehicle (80; 83) with an engine (14), which is cooled with a coolant in a cooling coil (19) regulated by the temperature controller (9), and a temperature sensor (16) measures the temperature (Tmmmß of the coolant, characterized in that the method comprises the following steps: A to regularly measure the temperature (Tmxmà of the coolant and to save at least one found local maximum temperature value (BMX), and B to set the opening temperature (Tqæn) to be one of the found local maximum temperature values (fl mx) that have been stored in memory. The method of claim 1, wherein step A further comprises the steps of: A1 regularly measuring the temperature (ï fi mmr) of the coolant and saving at least one found local minimum temperature value (E fi n) in a memory, A2 creating a memory space in which said found local maximum and local minimum temperature values are saved consecutively, A3 to determine the difference between any two consecutive temperature values saved in the memory space, and A4 to clear the memory space and restart the process for determining the aperture temperature (T @ aJ in step A if any difference in step A3 is outside a predetermined temperature range (TLW: Thmh), or to proceed to step B if 10 15 20 25 30 Bïlåïâš 778 21 all determined differences in step A3 are within the predetermined temperature range (TkW: Thgm). The method of claim 2, wherein a found local minimum temperature value (Tmn) is stored only in the memory of the down time (tdmm) that has elapsed between the previous local maximum temperature value (ï fi x) and the found local minimum temperature value (Tmm) is within a first predetermined time interval (e.g. ° m, 1 ° w: tdowrhhigh). The method of claim 3, wherein the past down time (tamm) is measured by a first counter (Ramm) which is reset to zero when a local maximum temperature value (Tmm) is found and which is counted up until the next local minimum temperature value (Tm fl) is found. The method according to any one of claims 1 ~ 4, wherein a found local maximum temperature value (Tmm) is only stored in the memory of the uptime (mm) that elapsed between a previous local minimum temperature value (On and the found local maximum temperature value (Bmx) is within a second predetermined tidSinterVall (tupgowituplhigh). The method of claim 5, wherein the elapsed time (mm) is measured by a second counter (Km) which is reset to zero when the local minimum temperature value (Tmm) is found and which is counted until the next local maximum temperature value (Tmax) is found. The method according to any one of claims 3 to 6, wherein all the saved temperature values @ H (tup, tdmm) is outside the corresponding first and second time intervals. A method for speed control of a fan (18) in a vehicle (80; 83) with a motor (14), which is cooled with a coolant in a cooling coil (19) with a cooler (19 ') and which is controlled by a temperature regulator (9), a temperature sensor (16) measures the temperature (fl mu fl) of the coolant, a cooling air flow (17) through the cooler (19 ') is controlled by the fan (18) to cool the coolant, characterized in that the method comprises the following steps: a) to determine an opening temperature (Tqßn) of the temperature controller (9), b) to regularly measure the temperature (ïhmwr) of the coolant, and to compare it with the determined opening temperature (TQEQ of the temperature controller (9), and c) to increase the speed of the fan (18) to control the velocity of the cooling air flow (17) if the temperature (Tmmm) of the coolant is higher than the set opening temperature (Twaà of the temperature controller (9). The method according to claim 8, wherein the step of determining the opening temperature (Tqæn) of the temperature controller (9) in step a) is performed using the method as defined in any one of claims 1 to 7. The method according to claim 8 or 9, wherein the speed of the fan (18) is reduced to a lower speed if the temperature (Tmmu) of the coolant is lower than the determined opening temperature (Tqæn) of the temperature regulator (9). 10 15 20 25 30 528 778 23 A method for estimating the efficiency of a charge air cooler (13) in a vehicle (80:33) having a motor (14): which is cooled with a coolant in a cooling coil (19) with a cooler (19 ') and which is regulated of a temperature regulator (9), a temperature sensor (16) measures the temperature (Tamm) of the coolant, and preheated air is fed into the charge air cooler (13), a cooling air flow (17) passes through both the charge air cooler (13) and the cooler (l9 ') for cooling the preheated air before supplying it to the engine (14), or cooling the coolant, characterized in that the method comprises the following steps: a) determining an opening temperature (Tqæn) of the temperature controller (9), bl) comparing a value of the temperature (Thmwr) measured by the temperature sensor (16) of the coolant with the determined opening temperature (Tqæn) of the temperature controller (9), and cl) to issue an indication that the estimated efficiency of the charge air cooler (13) is lower than a permissible limit value if temperature the temperature (Tmxm) measured by the temperature sensor (16) for the coolant is higher than a permissible value (Thin) compared to the set opening temperature (Twæd of the temperature controller (9). The method according to claim 11, wherein the step of determining the opening temperature (Tqæn) of the temperature controller (9) in step a1) is performed using the method as defined in any one of claims 1 ~ 7. The method according to claim 11 or 12, wherein an issued indication that the estimated efficiency of the charge air cooler (13) is lower than a permissible limit value, in step c1), is used to prevent a process from being performed to 5228 778 24 verify the operation of an external temperature sensor (11) in the vehicle (80; 83). The method according to claim 13, wherein the process of verifying the operation of the external temperature sensor (11) is performed if the opening temperature (Twag in step a1) could not be determined within a predetermined time (tlmg). The method according to any one of claims 11 to 14, wherein the method for speed control of a fan (18) in a vehicle as defined in any one of claims 8 to 10 is performed on the same thread. A computer program for determining the opening temperature (Tqæn) of the temperature controller (9) in a journey (80:83) with a motor (14), which is cooled with a coolant in a cooling coil (19) controlled by a temperature controller (9), and a temperature sensor (16) measures the temperature (Tmmm) of the coolant, in that code means, when characterized, executed in a control unit (15), adapted to receive signals from the temperature sensor (16), can execute the method according to any one of claims 1 ~ 7. A computer program for speed control of a fan (18) in a vehicle (80; 83) with a motor (14), which is cooled with a coolant in a cooling coil (19) with a cooler (19 ') and which is controlled by a temperature controller (9), a temperature sensor (16) measures the temperature (Tmmm) of the coolant, a cooling air flow (17) through the cooler (19 ') is controlled by the fan (18) to cool the coolant, characterized in that code means when executed in a control unit (15), adapted to receive signals from the temperature sensor (16), can execute the method according to any one of claims 8-10. A computer program for estimating the efficiency of a charge air cooler (13) in a vehicle (80; 83) having an engine (14) which is cooled by a coolant in a cooling coil (19) having a cooler (19 ') and which is regulated with a temperature regulator (9), a temperature sensor (16) measures the temperature (T fi mwr) hOS the coolant, and preheated air is fed into the charge air cooler (13), a cooling air flow (17) passes through both the charge air cooler (13) and the cooler (19 ') to cool the preheated air before supplying it to the engine (14), respectively to cool the coolant, characterized in that code means when executed in a control unit (15), adapted to receive signals from the temperature sensor (16), can execute the method according to any of claims 11-15. A computer program product comprising a computer readable medium and a computer program according to any one of claims 16 to 18, wherein the computer program is included in the computer readable medium. A control unit (15) for determining the opening temperature (Tqen) of the temperature controller (9) in a vehicle (80; 83) with a motor (14), characterized in that the control unit (15) comprises a memory unit (M) comprising a computer program according to claim 16. A control unit (15) for speed control of a fan (18) in a vehicle (80; 83) with a motor (14), characterized in that the control unit (15) comprises a memory unit (M) comprising a computer program according to claim 17. 10 15 5128 778 26 A control unit (15) for estimating the efficiency of a charge air cooler (13) in a vehicle (80:83) with a motor (14), characterized in that the control unit (15) comprises a memory unit (M) comprising a computer program according to claim 18. A vehicle (80; 83) provided with an engine (14), characterized in that the vehicle (80; 83) is further provided with a control unit according to any one of claims 20 or 21. A vehicle (80; 83) provided with an engine (14) with a connected charge air cooler (13) which provides cooled air to the engine (14), characterized in that the vehicle (80; 83) is further provided with a control unit according to claim 22.